A6-C5 Cooling Fans Query

[JMR1]

Hi All,
some info needed, if anyone can help. In the cooling system in my Audi 1.9 tdi, there are two fans on the radiator. One is a viscous coupling fan, and the 2nd fan is electric motor driven.
The viscous fan I presume is the main engine cooling fan, heat from the engine expands the wax in the coupling, and drives the fan. ( open to correction on this ) But what triggers the 2nd fan? I mean where is the switch located? I presume that this is a "back-up" fan for the main fan? Or does it have another function? AirCon maybe? In the wiring, how does it work? Is the feed continuously live, then drives the fan when the sensor earths when the water gets hot enough? Or is it a closed circuit, controlled via electronic unit or relay? And how is it triggered?
Thanks for your help,
All the Best,
Jim..

[ceilidhalfie]

Electric Fan is for air con. There is no external switch and it is two phases - one low and one high. Connector is underneath power steering reservoir cover. The electric fan is on low all the time until engine temp or air-con requires additional cooling over above viscous fan and low electric. The electric fan will then run at high setting.
I ran my Allroad for about 4 years before I notcied the electric fan had burnt out - sitting in a very hot car park in the south of France with the engine running and the air con on. The temp gauge beg an to rise! ... Back to mormal when the car moved off and the viscous fan was able to handle.
So unless you are in a hot climate (or in traffic jam on a hot day) you won't notice a dead electric fan. Being an owner who like to see everything working, I replaced my electric fan froom a source in Poland!

[JMR1]

Thanks ceilidhalfie,
Since I bought this car 2 years ago ( it was traded in because it was overheating) there has always been a problem. Thermostat, water pump, belts, engine sensor etc. In fact all the usual suspects were replaced !!!! Even then occasionally, temp gauge would shoot up, dash water red light flashing etc. Then just as quick.... all would return to normal. So while it did happen during the winter, it was not so much. Then with the rise in temp, it has started up to its old tricks again. For some strange reason, it will behave perfectly, say driving for 20 or 30 mins. Then after being switched off an parked for awhile.....when it is started again, up goes the temp. Will remain high for varying lengths of time, before just as quick returning to normal. Then while doing some other work on it, I wired the electric fan direct......dead as the dodo. So I got another fan (Also Polish LOL...... ) and I fitted it this morning. So far, no temp problems. The original fan in my Audi is single speed, 2 wires only feeding it. While fitting it, I saw a sensor switch in the bottom water jacket.......I presume that this switch is for the electric fan? As it happened, given the warm weather we are experiencing at the moment, the controls were set to LOW.....so when the ignition was switched on, the fan cut in immediately. So I cant help but think that this non working fan was at least part of my problem. One comment, instead of wiring the fan from the connection directly shortest distance between two point...it travels all round the fan housings.. serious skinned knuckle territory !!!! Anyway, over the next few days.....we will see if the problem has been fixed. With hind sight, I should have checked the fan the very first day.....
Thanks again, Ceilidhalfie.
Jim.

[bluezie]

Electric Fan is for air con. There is no external switch and it is two phases - one low and one high. Connector is underneath power steering reservoir cover. The electric fan is on low all the time until engine temp or air-con requires additional cooling over above viscous fan and low electric. The electric fan will then run at high setting.
I ran my Allroad for about 4 years before I notcied the electric fan had burnt out - sitting in a very hot car park in the south of France with the engine running and the air con on. The temp gauge beg an to rise! ... Back to mormal when the car moved off and the viscous fan was able to handle.
So unless you are in a hot climate (or in traffic jam on a hot day) you won't notice a dead electric fan. Being an owner who like to see everything working, I replaced my electric fan froom a source in Poland!

The electric fan on our 2.5 AKE must have burnt out, or a fuse popped, as I found some cowling plastic broken of and jamming it years ago, and it's never worked since. In normal conditions the car and aircon work perfectly. The only time I noticed a problem, was sitting in traffic in the summer, the aircon started to not cool the air, although the temperature gauge stayed normal. As soon as the car was moving again, the aircon kicked into life.
So UK temperatures not a problem, but South of France it needs to work!

[JMR1]

Hi me again...... despite having the electric fan working 10%, still have over heating problem, at least according to the dash gauges, but its clearly now an electrics problem. Temp gauge starts to rise moments after starting the engine, will rapidly hit 90 or 100 c, then just as quick, will drop back down to 60-70c, and slowly rise to its normal position of 90c. So I took it to a local indy who has VCDS, and got him to scan it, and everything showed up as normal, no faults... except "Climate and Comfort Module" fault. So after all the possible causes and solutions, seems that this module was faulty from day one......Its located under the carpet on the front passengers seat, and normally these are damaged by water leaking into the foot well, but when I bought the car, I checked all the drains and the plenum chamber, cabin filter etc......all bone dry. Nonetheless, at some stage it must have come in contact with water. So now the question is, can it be cleaned and restored, or is replacement the only option? If it has to be replaced, does it have to be programmed into the existing system? or will the accept it as is? ( given modern electronics.....I'm not too optimistic about this !!!!) Seems that this module feeds a lot of info to the dash ( hence Temp gauge behaving erratically) plus it has other functions too, and one side effect seems to be that the electric fan is now running continuously as soon as the engine is started. Any one have to replace this unit, and if so, what to watch out for?
Thanks in advance for any help you may be able to give..
All the Best, Jim.

[ceilidhalfie]

You sure the coolant is overheating?? I seem to replace my coolant temp sensor about every 3 years - sensor works for a while but then takes ages to move off bottom and would sit on 70/80 degrees. Also had one sensor that behaved like yours - would rise to 90, drop to zero, rise to 70 etc. New sensor fixed the problem.
until a few weeks ago, the last sensor just sat 70-80. Eventually got round to replacing and now gauge works perfectly - obediently rises to 90 after a few minutes driving.
So before you go spending ££££s and ripping up carpets, try replacing the CTS (with a decent qualiy one - it MIGHT last longer). Tip when replacing CTS ( if it is positioned as on my Allroad), tie the clip to the lift mount of the engine with a length of wire. You can then flick the clip off without the sodding thing going down into the bowels of the engine - and just reuse this clip when inserting the replacement CTS.

[JMR1]

Thanks Ceilidhalfie, the CTS was replaced about 7 mths ago, genuine VW/AUDI dealership supplied, so for now at any rate, should be OK. I agree that replacing the CCM and what that entails is a job best avoided, if possible, especially as all the other items governed by this module are working fine...but still it was the only fault thrown by the VCDS, everything else was A-OK. So the indy reckons that this is the cause of the temp fluctuations,,,, BUT,,,,,,,, to day, I drove 50 miles mixed road /high way, and temp behaved impeccably,, steady 90c all the way. Stopped for 5-6 hrs, then drove another 5 miles, with the temp hitting 120c for the last mile, red dash warning light flashing, and beeping like mad. So I stopped in a car park and lifted the bonnet....everything " Cool", literally, top water jacket hot but not excessively so. Switched everything off, and was parked for the next 5 hours, then started back home again. Everything was Ok for the first 2 miles or so, then temp hits the 120c , with flashing dash lights and warning beeper, here we go again. As I was on the highway and very reluctant to stop, continued on hoping that it would return to normal, but no such luck. I desperation and frustration, I hit the top of the dash panel....hard !!! WOW.. everything returned to normal instantly. Thereafter, every time it even looked like it was thinking about moving fractionally above the 90c, I hit it again !!! It worked, so now I can safely say that after all the possibilities have been tried, it is the dash itself which is the problem. So I plan on removing it, and cleaning it with some gentle pressure from an airline, then re-installing it and seeing what will happen.
Will keep you posted, but for now, I am a happy man !!!
All the Best,
Jim

[JMR1]

More on the over heating problem, if removing and cleaning the dash panel does not work, what are the complications (if any) of replacing it with a dash set from a scrap A6? Would the replacement set need to be programmed with VCDS?
Any advice / comments are more than welcome...
All the Best,
Jim

[JMR1]

Fan Query,,,,as I understand it, the electric fan on the radiator, should only run intermittedly, on my A6, it is running full time. So I am guessing here, but there has to be a sensor or switch controlling it. Anyone know where it might be located? Or is there another possible cause?
Thanks for your help,
Jim

[rich81]

Hi Jim, do you have the A.C. switched on as it will run continuously when the A.C. is on to cool the evaporator radiator. Otherwise, there is a temp switch somewhere that will bring it on for high coolant temp

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